Many good dietary advices exists but experience shows that it is not an easy matter to get people consuming more soluble dietary fibres even though it has long been realized, that this is beneficial to health, especially if one suffers from diabetes or obesity.
For regulating food consumption different dietary fibres are commonly used. Dietary fibres are grouped into 2 types: soluble and insoluble fibres. The insoluble dietary fibres are present in coarse bread and starchy vegetables. Examples of insoluble fibres comprise cellulose, hemicellulose, lignin and pectin. The soluble fibres are present in fruit and vegetables. Examples of soluble fibres comprise guar, dextran, alginate, starch, amylose, amylopectin, xanthan, pullulan, carrageenan and gellan.
US 2004/0228903 discloses a liquid edible composition having a pH of more than 5 and containing pectin or alginate together with a calcium salt. The calcium salt may be present in an amount exceeding its maximum solubility in the edible liquid, however it will dissolve in the stomach under the influence of the pH reduction and/or the rise in temperature. Typical calcium salts are CaC03 and CaHP04. The increasing calcium concentration will stimulate the pectin and/or alginate gellation as calcium ions and the polysaccharides form a rigid matrix. The alginate or pectin used has a viscosity below 50 cP at a shear rate of 100s″1.
WO 2005/020717 and WO 2005/020719 relate to a food product which in addition to alginate and insoluble calcium salt also comprises protein. The food product may be a liquid or a spoonable edible product. The alginate preferably has a molecular weight of at least 0.5×105 and a guluronic acid content of at least 65%.
The rigid matrix is formed when calcium ions is complexed with homogeneous blocks of guluronic acid in alginate or pectin to form an “egg box” structure. Control of the calcium concentration through out the gelling process is crucial for a uniform gel to evolve. If the initial concentration of calcium is too high the polysaccharide will precipitate rather than forming a gel. The conditions may be difficult to control in the stomach due to interpersonal differences and pre- or post-eaten food products.
Calcium-induced gelation implies that a high amount of calcium salt must be present in the product before consumption. In the drink according to US 2004/0228903, WO 2005/020717 and WO 2005/020719, the calcium salt is present as an insoluble salt. Since the drink prior to ingestion generally is desired to have a low viscosity to obtain consumer acceptance the insoluble calcium salt will precipitate during storage. Apart from the inconvenience of shaking the drink before consumption an inhomogeneous product further has the disadvantage that the consumer may not obtain the calcium salt in a proper dose for an optimal gelation to progress.
U.S. Pat. No. 5,324,526 discloses an alginate-containing food product aimed at reducing the activity of insulin to synthesize fats from glucose. The alginate is used as a dietary fibre and is produced by degradation of commercially available alginate by a certain pressure and temperature scheme. Alginates with the desired ability to reduce glucose in blood and at the same time stabilise the amount of insulin have an average molecular weight of 50.000. If the alginate is shorter, i.e. around a molecular weight of 10.000 the alginate show no tendency to reduce the blood glucose. For an alginate of a molecular weight of 100.000 the tendency to reduce blood glucose is similarly reduced compared to the alginate having a molecular weight of 50.000. Probably due to the production method, the viscosity of the alginates is low. Thus, a typical alginate of an average weight of 60.000 has at 30° C. in an aqueous concentration of 5.2-5.3% a viscosity of 13 cP.
The low viscosity results in a poor gel strength of the food product when the food product is ingested and contacted with the acid in the stomach. If the gel strength is insufficient the physiological stimulation of a feeling of satiety will not be so pronounced.
It is the object of the present invention to provide a diet product which avoids some or all of the disadvantages of the prior art. Notably, it is desired to provide a diet product which before ingestion has a viscosity low enough for consumer acceptance while at the same time when contacted with the gastric juice being able to produce a gel strength sufficient for a consumer to feel satiety.